The most widely used systems for misfire detection are those wherein short-term fluctuations of the rpm of the internal combustion engine are investigated. However, it is problematic in these systems that such rpm fluctuations are generated not only by misfires but also by reaction forces which operate from the drive wheels on the engine via the drive chain. Accordingly, numerous system variations concerning the detection and evaluation of rpm fluctuations have become known. Reference can here be made, for example, to U.S. Pat. No. 5,044,195 wherein numerous publications with respect to the state of the art are delineated.
U.S. patent application Ser. No. 07/819,079, filed Jan. 10, 1992, (now U.S. Pat. No. 5,231,869) discloses an arrangement wherein the detection of misfires is interrupted at the start of pregiven operation conditions of the motor vehicle for so long until the pregiven conditions are no longer satisfied. The jarring of the motor vehicle because of externally acting forces is listed as one of the pregiven conditions. The jarring can, for example, be determined with the aid of signals from an acceleration sensor. Such a system is formed on the basis of the realization that many short-term rpm fluctuations of the wheels occur when a motor vehicle runs over a rough roadway. These rpm fluctuations of the wheels react on the rpm of the engine via the drive chain even though the elasticity thereof attenuates said rpm fluctuations.
From U.S. Pat. No. 4,929,034, it is known to change the performance of an anti-locking brake control system in dependence upon the condition of a roadway. For this purpose, a numerical value is added to a sum for each occurrence of a wheel acceleration of at least a pregiven quantity. This sum is again reduced according to a pregiven function. The actual value of the sum is used as a value for adjusting the performance of the system.